1. Field of the Invention
The present invention is generally related to a hydraulic steering cylinder control system and, more particularly, to a control system which uses two 3-way valves to control the rate of flow of hydraulic fluid to and from two sides of a piston and also selects the appropriate side of the piston that is supplied with pressurized oil and the side of the piston from which oil is drained in order to facilitate accurate and smooth movement of the piston within its hydraulic cylinder casing.
2. Description of the Related Art
Many types of hydraulic cylinder control systems are known to those skilled in the art. In addition, hydraulic cylinders used to actuate steering movements of vehicles are known to those skilled in the art. Some steering cylinders are used to control the movement of a marine vessel in response to changes in the position of a steering wheel which is manually movable. Many different types of hydraulic valves are known to those skilled in the art. Proportional valves have been used in various applications. Marine propulsion devices can be outboard motors, sterndrive systems, pod-type propulsion devices that extend downwardly through the bottom surface of a water craft hull, or inboard marine propulsion systems that are steered through the use of a rudder.
U.S. Pat. No. 3,654,889, which issued to Bergstedt on Apr. 11, 1972, describes a hydraulic system for a boat drive. The system for steering and tilting an outboard drive unit for a boat includes a pump, a steering subsystem including a double acting cylinder and piston connected to provide steering movement to a steerable part of the unit and provided with hydraulic liquid from the pump and a trimming and tilting subsystem including a cylinder and piston assembly provided with liquid from the steering subsystem.
U.S. Pat. No. 3,680,583, which issued to Clair on Aug. 1, 1972, describes an automatic sequential operated valve. An automatic four-way valve hydraulically operated for extending and retracting a refuse compaction cylinder is described. It senses a pressure build-up as the trash is compacted and releases a pressure responsive detent allowing a spring to drive the valve spool of the primary valve to a return position. It allows the cylinder to retract until it reaches the end of its stroke whereupon a pressure build-up causes a pilot cylinder to move the valve spool to the neutral open center position.
U.S. Pat. No. 4,006,664, which issued to Brown on Feb. 8, 1977, describes a steering system including tandem hydraulic cylinders with self-synchronization. It is suitable when front and wheel rears are hydraulically steered, each set by its own hydraulic cylinder. The two cylinders are connected in hydraulic tandem so that the same angularity of steering will be imparted to both sets of wheels.
U.S. Pat. No. 4,016,949, which issued to Plate et al. on Apr. 12, 1977, describes a hydrostatic load sensitive regenerative steering system. A control valve operated by the steering wheel to selectively connect a variable displacement pump for operating a hydraulic cylinder in each of two directions to steer the wheel is described. The hydrostatic system is regenerative in steering of the hydraulic cylinder in one direction since both sides of the hydraulic cylinder are connected to the high pressure input line in steering in one direction.
U.S. Pat. No. 4,365,645, which issued to Wohlrab on Dec. 28, 1982, describes a three-way flow regulating valve. It comprises a two-position two-ported throttle valve inserted between an inflow conduit and an outflow conduit and a pressure relief valve connected to the inflow conduit at an upstream point thereof and at a downstream point proximate to an intake port of the throttle valve. A servo valve is connected in parallel to the throttle valve via small diameter pressure transmission channels extending to the intake port and to the output port of the throttle valve. Upon a jump in the pressurization of the inflow conduit, for example due to the activation of an auxiliary pump, the pressure relief valve opens. It closes again only upon an equalization of the pressure throughout the inflow conduit.
U.S. Pat. No. 4,449,470, which issued to Rump on May 22, 1984, describes a hydraulic control package for a marine steering system. It has a steering helm pump with port and starboard fluid outlets and a return inlet for hydraulically actuating a piston in a hydraulic cylinder having port and starboard inlets for moving the piston back and forth in the cylinder in response to fluid delivered from the helm pump. A fluid reservoir is closed and pressurized with air and is defined by an open ended tube having a cap sealing the top end of the tube and a valve body sealing the bottom end of the tube. The valve body houses the control valve means for controlling the fluid flow in the system between the helm pump and the actuating cylinder.
U.S. Pat. No. 4,458,775, which issued to Lestradet on Jul. 10, 1984, describes an apparatus for guiding a vehicle. It comprises a detector sensing deviation of the heading of the vehicle relative to a predetermined direction and it produces an electrical deviation signal. It also comprises a hydraulic piston and cylinder device for steering the vehicle wheels and control means responsive to the deviation signal.
U.S. Pat. No. 4,659,315, which issued to Bland et al. on Apr. 21, 1987, describes a hydraulic system for marine propulsion devices. It comprises a gimbal housing adapted to be fixedly attached to the transom of a boat and including an end plate adapted to be generally aligned with the boat transom and having an opening, opposite sides, and a rear surface. The gimbal housing also includes a first generally vertical side member extending rearwardly from one side of the end plate and a second generally vertical side member extending rearwardly from the other side of the end plate. A gimbal ring is pivotally connected to the gimbal housing for pivotal movement relative to the gimbal housing about a generally vertical steering axis.
U.S. Pat. No. 4,710,141, which issued to Ferguson on Dec. 1, 1987, describes a marine propulsion device power steering system. It includes a propulsion unit mounted for tilting movement about a generally horizontal tilt axis and for pivotal steering movement about a vertical steering axis. It also comprises a power steering system adapted to operably connect an actuator to the propulsion for increasing the steering force applied to the propulsion unit by the actuator.
U.S. Pat. No. 4,789,036, which issued to Haas on Dec. 6, 1988, describes a hydraulic steering device. It is intended for changing the speed and direction of a hydraulically operated track vehicle. The hydraulic control system is equipped with a feed pump for the control fluid and with hydraulic undercarriage pumps. The undercarriage pumps comprise regulating cylinders and are subjected to the control fluid and intended for adjusting the pump pivoting angle.
U.S. Pat. No. 4,919,064, which issued to Ehluss et al. on Apr. 24, 1990, describes a hydraulic system for shift rudder roll stabilization and steering. It comprises a constant delivery pump, a pressure accumulator, and a valve gear unit. While the valve is opened the hydraulic fluid is delivered by the pump in the accumulator and when the valve is closed the pump fills up the accumulator to maximum working pressure. The valve gear unit comprises a proportional control valve for controlling period, direction and flow rate of the hydraulic fluid to the steering engine and a load compensation device for controlling the returning flow returning via the proportional control valve for compensating for irregular loads from the waves or the sea against the rudder.
U.S. Pat. No. 5,092,801, which issued to McBeth on Mar. 3, 1992, describes a hydraulic steering assembly for outboard marine engines. The assembly is connected to the tiller arm of an outboard marine engine and includes a piston rod supporting for arcuate movement about the tilt axis while remaining parallel thereto. A hydraulic cylinder travels along the piston rod. An arm extends from the cylinder to a first pivotal member establishing a first pivotal connection about an axis parallel to the tilt axis. A rigid link extends between the first pivotal member and a second pivotal member.
U.S. Pat. No. 5,207,245, which issued to Maranzano on May 4, 1993, describes a solenoid valve and a valve calibrating method. The valve has a paramagnetic valve body and a ferromagnetic adjustable end stop connected by a ferromagnetic tubular sleeve and forming a housing defining a valve chamber containing an axially elongate generally cylindrical ferromagnetic solenoid plunger supported for axial reciprocal movement between a pair of axially opposed valve seats.
U.S. Pat. No. 5,228,405, which issued to Merten on Jul. 20, 1993, describes a power steering system. It has a propulsion unit, including a steering arm, to effect steering movement thereof about a steering axis and an operator actuable steering helm. A first actuable steering member, such as a mechanical push-pull cable is operably connected to the steering helm and actuated in response to steering actuation at the helm.
U.S. Pat. No. 5,233,861, which issued to Gore et al. Aug. 10, 1993, describes an apparatus and method for in situ calibration of a metering device. A calibrated gas source and inlet are provided. Connected to the calibrated gas source is a first three-way valve. The first three-way valve is connected to an inlet of the metering device with an outlet connected to a second three-way valve. The second three-way valve is connected to both a reaction chamber or an exhaust. A calibration gas is allowed to flow through the calibration inlet, through the first three-way valve, through the metering device, and through the second three-way valve so as to calibrate the metering device to the calibrated gas source.
U.S. Pat. No. 5,266,060, which issued to Onoue on Nov. 30, 1993, describes a steering device for a marine propulsion device. It provides an improved apparatus for controlling the steering of a watercraft. Specifically, the steering device includes a push-pull cable steering arrangement which has a portion located along the rear of the watercraft. Such rearward portion is disposed for reciprocal movement within a cylindrical cable guide. The steering device also includes a hydraulic power assist arrangement which includes a hydraulic cylinder having a movable piston and associated piston rod contained therein.
U.S. Pat. No. 5,289,841, which issued to Maranzano on Mar. 1, 1994, describes a solenoid valve and valve calibrating method. A plunger is biased toward seating engagement with an associated one of the seats and is movable out of seating engagement with the one seat and into seating engagement with the other seat in response to energization of a surrounding solenoid coil. An annular ferromagnetic flux ring disposed adjacent one end of the coil cooperates with a diametrically enlarged portion of the plunger to define a portion of a flux path. The position of the end stop relative to the sleeve is adjusted during manufacture to set the clearance between the valve plunger and the one valve seat thereby enabling accurate valve calibration.
U.S. Pat. No. 5,303,793, which issued to Kato et al. on Apr. 19, 1994, describes a steering apparatus of rack-and-pinion type that comprises an input shaft steered by a driver, an output shaft operatively connected to a rack bar through a rack and pinion gear mechanism, a hydraulic cylinder operatively connected to the rack bar, and a rotary valve operatively connected to the input shaft.
U.S. Pat. No. 5,387,142, which issued to Takayanagi et al. on Feb. 7, 1995, describes a power steering device for an outboard engine. It has a hydraulic cylinder unit for angularly moving a steering arm of the outboard engine, the hydraulic cylinder unit having a piston rod connected to the steering arm, and a directional control spool valve for supplying a hydraulic pressure to the hydraulic cylinder unit to move the piston rod.
U.S. Pat. No. 5,427,045, which issued to Fetchko on Jun. 27, 1995, describes a steering cylinder with integral servo and valve. The steering apparatus for a marine craft includes an actuator assembly including a hydraulic steering actuator. The steering actuator is operatively connected to the tiller of the craft. A hydraulic servo actuator is mounted on the steering actuator. The servo actuator is permitted limited axial displacement relative to the steering actuator. The servo actuator is operatively connected to the steering actuator. The servo valve is mounted on the actuator assembly and has ports for receiving pressurized hydraulic fluid.
U.S. Pat. No. 5,449,186, which issued to Gerl et al. on Sep. 12, 1995, describes a rear wheel steering system. An actuating system includes a differential hydraulic cylinder containing a piston and a piston rod connected to one side of the piston. A first or head chamber is defined in the cylinder and is bounded by the one side of the piston to which the piston rod is not connected. A second or rod chamber is also defined in the cylinder and is bounded by the other side of the piston to which the piston rod is connected. An actuatable assembly is provided that is adapted to be connected to either the hydraulic cylinder or the piston rod. Finally, a proportional control valve is provided which is adapted to actuate the hydraulic cylinder by controlling the amount of fluid supply to the first chamber wherein the supply pressure is connected to the second chamber.
U.S. Pat. No. 5,454,291, which issued to Ulm et al. on Oct. 3, 1995, describes an electrohydraulic regulating device having pulse width modulated valves with an adjusting signal. An electrically actuating control valve controls the hydraulic fluid flow to the adjusting cylinder. At least one electrically actuated switching valve blocks or admits a hydraulic fluid flow. A control unit generates control signals for the control valve and the switching valve. The regulating circuit supplies a pulse width modulated regulating signal for regulating a mean current of the control valve.
U.S. Pat. No. 5,503,098, which issued to Bohlin on Apr. 2, 1996, describes an air purging device for hydraulic boat steering arrangements. It contains a hydraulic pump actuated by a boat steering wheel and has first and second fluid inlet/outlet ports, a hydraulic piston cylinder device with first and second chambers on either side of the piston and first and second hydraulic circuits between the inlet/outlet ports of the pump and corresponding inlet/outlet ports to the respective chambers. A valve unit can be coupled into the respective connection between the inlet/outlet port of the respective chamber and the inlet/outlet port of the pump, via which valve unit air in the fluid can be released.
U.S. Pat. No. 5,505,275, which issued to Phillips on Apr. 9, 1996, describes a power steering system for a motor vehicle having a power cylinder with the piston mounted in the power cylinder which divides the power cylinder into first and second chambers. The steering system includes a valve assembly having a rotary input member and a valve sleeve and first and second pairs of open center input valves, each having an inlet and an outlet. The inlets of the input valves are fluidly connected to the pump output. The valve assembly further includes a pair of closed center input valves and a normally closed bypass valve.
U.S. Pat. No. 5,542,286, which issued to Wang et al. on Aug. 6, 1996, describes a method and apparatus for correcting flow and pressure sensor drift in a gas chromatograph. At a convenient time when the chromatograph is not being used for analysis, the input valves controlling the input into the chromatograph are shut, reducing internal flow to zero. The indicated rate of flow is then measured using the flow sensor. If the value measured by the flow sensor during the test is different than the originally calibrated offset by some predetermined amount, then the newly measured value replaces the stored offset value.
U.S. Pat. No. 5,605,109, which issued to Merten et al. on Feb. 25, 1997, describes a power steering system. It includes a hydraulic fluid cylinder-piston assembly and is actuated in response to steering actuation at the steering helm. It has controls for maintaining anti-feed back upon a failure in the fluid source including a valve to establish fluid communication between a fluid source for the cylinder-piston assembly and the chamber in the assembly to either side of the piston thereby maintaining the chamber substantially full of hydraulic fluid during steering to effect movement of the piston upon steering actuation.
U.S. Pat. No. 5,802,848, which issued to McClendon et al. on Sep. 8, 1998, describes a hydraulic system for a motor vehicle. It includes a power steering pump, a reservoir, a steering assist fluid motor, and a second fluid motor for a radiator cooling fan. A flow control valve remote from the power steering pump divides the total fluid flow from the power steering pump into a high flow branch and a low flow branch.
U.S. Pat. No. 5,896,943, which issued to Christensen on Apr. 27, 1999, describes a hydraulic control system for work vehicles. The system includes a control unit to control the steering wheels of a vehicle via a cylinder and a priority valve which by a first load-sensing system controls the pressure fluid flow to the control unit and to a subsequent proportional valve group. By a second load sensing system the proportional valve group controls the pressure fluid flow to secondary hydraulic motors or work cylinders to control the work tools of the vehicle.
U.S. Pat. No. 6,067,782, which issued to Diekhans on May 30, 2000, describes an electrohydraulic steering system. The system includes manual steering and automatic steering modes which can be activated by a switch. The system has a hydraulic steering cylinder for displacement of the steering wheels, at least one sensor for determining the wheel angle actual values, at least one electrically operated hydraulic control valve which regulates admission of hydraulic fluid to the steering cylinder and at least one automatic steering signal transmitter for generating electrical steering signal nominal values of the wheel angles.
U.S. Pat. No. 6,138,596, which issued to Gonring et al. on Oct. 31, 2000, discloses a damped steering mechanism for a watercraft. A hydraulic damper is provided for a steering system such as that of a boat or watercraft. A manually movable steering mechanism, such as the steering wheel, is connected to a piston and cylinder combination in such a way that rotation of the steering wheel causes relative movement between the piston and cylinder. Hydraulic fluid is disposed within the cylinder in such a way that movement between the cylinder and piston requires the hydraulic fluid to move from one portion of the cylinder to another portion of the cylinder. This fluid movement is conducted through a conduit which can be external to the cylinder or internal to the cylinder and extending through the piston.
U.S. Pat. No. 6,269,903, which issued to Bohner et al. on Apr. 7, 2001, describes a steering system for a vehicle. High functional reliability for a vehicle steering system that can be switched between a normal mode with a steer-by-wire level and an emergency mode with a fall back level is achieved by providing that the fall back level has a hydraulic system which contains a manual-side double-acting piston-cylinder unit which is actuated with a steering handle. The unit is positively coupled hydraulically to a wheel-side double-acting piston-cylinder unit which actuates steered vehicle wheels.
U.S. Pat. No. 6,378,302, which issued to Nozawa et al. on Apr. 30, 2002, describes a hydraulic circuit system. A hydraulic line slit formed in a valve body of a flow distribution valve, a control chamber, and a hydraulic line are connected to a signal transmitting hydraulic line. A lap portion is formed in the hydraulic line slit, the lap portion having a check valve function with a lap amount when the valve body is in a cut off position. A two-position, three-way valve is disposed in the hydraulic line. The valve connects the control chamber of the flow distribution valve to only the signal transmitting hydraulic line when an external signal is not applied and to both the signal transmitting hydraulic line and a lower-pressure detecting hydraulic line which is connected an outlet passage of a flow distribution valve on the side of a hydraulic actuator when the external signal is applied.
U.S. Pat. No. 6,612,335, which issued to Assa et al. on Sep. 2, 2003, describes a three-way control valve. It comprises a body formed with an inlet port for connecting to a pressurized supply line, a first outlet port for connecting to an outlet line and being in flow communication with the inlet port, a gate intermediate the inlet port and the first outlet port, dividing the body into an inlet chamber and an outlet chamber, the body further comprising a second outlet extending from the outlet chamber, and a control chamber fitted with a deformable diaphragm sealingly engagement with the gate so as to prevent flow between the inlet port and the first outlet port.
U.S. Pat. No. 6,821,168, which issued to Fisher et al. on Nov. 23, 2004, discloses a power steering system for a marine vessel. An outboard motor is provided with an internally contained cylinder and movable piston. The piston is caused to move by changes in differential pressure between first and second cavities within the cylinder. By adding a hydraulic pump and a steering valve, the hydraulic steering system described in U.S. Pat. No. 6,402,577 is converted to a power hydraulic steering system by adding a hydraulic pump and a steering valve to a manual hydraulic steering system.
U.S. Pat. No. 6,896,092, which issued to Stall on May 24, 2005, describes a hydraulic steering device. It has a steering angle transmitter in communication with a steering valve which, as a function of the actuation of the steering angle transmitter, controls the communication between the steering drive with a hydraulic pressure source and a reservoir and a correction device. The correction device provides a synchronization of the position of the steering angle transmitter with the position of the steering angle drive when the steering drive or steering angle transmitter is in a reference range and the position of the steering angle transmitter and/or of the steering drive varies from the reference range.
U.S. Pat. No. 6,955,114, which issued to Stockner et al. on Oct. 18, 2005, describes a three-way valve and electrohydraulic actuator using the same. It relates to high speed control valves which are especially applicable for use in fuel injection systems. Reducing a valve with a quick response time within acceptable packaging constraints and with a structure that allows the valve to be mass produced with consistent performance between valves is problematic. By moving flow restrictions within the valve away from the valve seats, flow forces on the valve member can be reduced while possibly also permitting a reduction in the necessary travel distance of the valve member to improve response time and other performance characteristics.
U.S. Pat. No. 7,037,152, which issued to Sasayama et al. on May 2, 2006, describes a steering apparatus for an outboard marine engine. A tilt tube extends along a horizontal tilt axis. A steering hydraulic cylinder slides along a piston rod which extends in parallel with the tilt axis. An eccentric link shaft is positioned between the tilt tube and the piston rod and extends in parallel with the tilt axis. A pair of linking means supports the tilt tube, link shaft and piston rod. The distance between the tilt tube and the piston rod is shorter than the sum of the distance between the tilt tube and the link shaft and the distance between the link shaft and the piston rod.
U.S. Pat. No. 7,156,708, which issued to Dudra on Jan. 2, 2007, describes a marine steering assembly with an integrated pivot pin. An assembly for applying a force to a tiller of a marine outboard propulsion unit is described. The steering assembly comprises a hydraulic steering actuator including a cylinder and an elongated piston rod. A pivot member is pivotally mounted on the tiller of the propulsion unit for pivoting about a first link axis which is parallel to the steering axis. There is a pair of actuator arms, each actuator arm being connected to the cylinder and having a portion extending radially outward with respect to the piston rod axis.
U.S. Pat. No. 7,160,163, which issued to Gai on Jan. 9, 2007, describes a steering device for use with marine outboard engines. The steering device has an end for fastening to transoms of watercrafts. The motor/propeller assembly is mounted to the end to rotate about a substantially vertical steering axis. A closed hydraulic circuit has at least one pump driven by the steering unit and at least one double-acting cylinder which is slidably on at least one coaxial rod. The rod sealingly projects out of the cylinder head and carries a separating piston which divides the cylinder into two variable volume chambers. At least one of the inlet/outlets of at least one of the two chambers is formed by the rod. The rod has an axial hole extending from its outer end to one or more ports for communication with corresponding chambers of the cylinder. The ports are arranged to be adjacent to the piston side turned toward the cylinder head from where the rod projects.
The patents described above are hereby expressly incorporated by reference in the description of the present invention.
As described above, many types of steering systems are known to those skilled in the art. Some of these steering systems are used on watercraft in order to move a propulsion device or rudder about a generally vertical steering axis. When a hydraulic cylinder and piston are used to actuate a steering device, there is an inherent problem that exists because of the presence of a single steering rod attached to one side of the piston. Because of this attachment, the surface area on the rod-bearing side of the piston is less than the surface area on the opposite side of the piston. If the flow of hydraulic fluid is generally constant, the resulting effect is that the piston will move in a retracting direction at a faster rate than in the actuating direction. If the hydraulic cylinder device has a piston rod extending from both sides of the piston, this problem does not exist. However, in hydraulic cylinder devices that have one piston rod attached to one side of the piston, the actuation of the piston in one direction will naturally be at a slower rate than the retraction of the piston in the other direction. This situation exacerbates the problem of maintaining very accurate positioning of a steering cylinder piston. It would therefore be significantly beneficial if a steering system could be provided in which the control of fluid flow to both sides of the piston is maintained in an accurate manner.